Micropile Underpinning Project at Washington Middle School, Evansville, IN

Project Overview:

During renovations at Washington Middle School, the building was found to be experiencing differential settlement. Soil borings revealed fill material beneath the foundation, raising concerns about the best approach for stabilization. This is when micropile underpinning presented itself as a solution.

Initially, the design engineers recommended steel resistance underpinning and helical underpinning. However, upon reviewing the soil data, United Dynamics, Inc. (UDI) identified potential challenges:

  • Helical piers could encounter cobbles or floaters in the fill, preventing proper installation.

  • Steel resistance piers could be compromised due to the unstable fill material.

To ensure a safe and effective solution, UDI proposed the use of small-diameter hollow bar micropiles.

Why Micropiles?

Image of a micropile manufactured by ECP.

Micropiles offered several advantages for this project:

  • They could penetrate through the cobbled fill into stable material below.

  • Passive installation provided a greater factor of safety in both strength and performance.

  • The system allowed for a quick, economical solution with minimal crew.

Project Execution

UDI implemented the micropile solution using:

  • Titan 40/20mm hollow bar micropiles

  • Earth Contact Products MP 350 Underpinning Brackets (75,000–99,000 lbs capacity)

Installation Steps:

  1. The site was excavated, and footings were prepared on day one.

  2. Brackets were mounted to the footings.

  3. Micropiles were installed by coring and grouting simultaneously, drilling 35′ through the cobbled fill into stable strata.

  4. Upon completion, the structure was stabilized and lifted using the MP350 bracketing system.

Outcome:

  • Project completed in just over three days with a three-person crew.

  • Achieved a cost-effective, reliable solution for a complex underpinning scenario.

Conclusion

UDI’s expertise in micropile underpinning techniques allowed them to provide a safe, economical, and timely solution for Washington Middle School’s differential settlement issue.

Project Team:

General Contractor: Danco Construction Co.
Micropile Installer: United Dynamics, Inc.
2555 Cannon St, New Albany, IN
800-359-4471

Looking for a contractor for a similar project in your area? Find your contractor using our Locator!